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Study debunks pop-psychology idea that people are either right- or left-brained

A team of University of Utah researchers spent two years reviewing the brain scans of 1,011 individuals aged 7 through 29 years.

Until early in the 20th century, many people — including many scientists — believed that bumps and indentions on the skull helped determine an individual’s personality.

That idea — phrenology — has been thoroughly discredited, of course. And now it appears it’s time to debunk a more recent popular assumption about the brain and personality: the idea that individuals tend to be either more creative or more analytical depending on which side of their brain they use the most.

For a new, large brain-imaging study, published last week in the journal PLOS ONE, has found no evidence that people are predominantly right-brained (creative) or left-brained (analytical).

In other words, differences in cognitive (thinking) style have nothing to do with one hemisphere of the brain being used more often than the other.

A detailed analysis

It was a very thorough study. A team of University of Utah researchers spent two years reviewing the brain scans of 1,011 individuals aged 7 through 29 years. The scans, collected as part of the International Neuroimaging Data-Sharing Initiative, were made while the participants lay in a magnetic resonance imaging (MRI) scanner for five to 10 minutes.

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Brain-function lateralization was measured for each participant. (Lateralization refers to the specialization of certain mental processes to primarily one hemisphere of the brain.) The researchers then broke the brain down into 7,000 separate regions and analyzed which regions of each participant’s brain showed the most lateralization.

They found brain-connection patterns that were strongly correlated with either the right or the left hemisphere of the brain. Connections associated with language and the perception of internal stimuli (those produced by the body) tended to occur in the left hemisphere, for example, while connections associated with the perception of external stimuli (those produced by the environment outside the body) were more likely to appear in the right hemisphere. But none of the participants’ brains demonstrated a “preference” for one hemisphere over the other.

No gender preference

Interestingly, the study also found no gender preference for a particular hemisphere. (Part of the pop-psychology myth about personality and “brained-ness” is that women are more right-brained than men.)

“It’s absolutely true that some brain functions occur in one or the other side of the brain,” said  Dr. Jeff Anderson, a University of Utah neuroscientist and one of the study’s authors, in a press statement. “But people don’t tend to have a stronger left- or right-sided brain network. It seems to be determined more connection by connection.”

Dr. Jeff Anderson discusses theories of left brain-right brain dominance.

His research may have finally relegated the idea that individuals are either right- or left-brained to the realm of pseudoscience, but Anderson says the study’s findings have even more important implications.

“We want to use this to understand neurodevelopmental conditions like autism and Down’s syndrome,” he says in a video released with the study. “We think that by understanding variations in which functions are truly lateralized to which sides that we can develop markers to understand these disorders and hopefully develop better treatments or see if the patients are responding to the treatments we have.”

PLOS ONE is an open-access journal, so you can read the study in full on the publication’s website.